Peptide capable for binding to iridium

Abstract

The present invention provides a novel peptide capable for binding to iridium. The peptide consists of an amino acid sequence represented by SQMMGHMGHGNMNHMNHGGKFDFHH (seq ID NO: 01).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Japanese Patent Application No.: 2012-089787 filed Apr. 11, 2012, the content of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

Technical Field

The present invention relates to a peptide capable for binding to iridium.

SUMMARY

Technical Problem

The purpose of the present invention is to provide a novel peptide capable for binding to iridium.

Solution to Problem

The present invention is a peptide capable for binding iridium, wherein

the peptide consists of an amino acid sequence represented by SEQ ID NO: 01.

The present invention is a method for binding a peptide to iridium, the method comprising steps of:

mixing the iridium with a solution containing the peptide consisting of an amino acid sequence represented by SEQ ID NO: 01 so as to bind the peptide represented by an amino acid sequence represented by SEQ ID NO: 01 to the iridium.

Advantageous Effects of Invention

The present invention provides a novel peptide capable for binding to iridium.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic view of a two-component composite 103 of avidin 101 and biotin-PEG12 (reference number: 102) according to the comparative example 1, which is included in the experiment 1.

FIG. 2 shows a schematic view of a composite 106 of avidin 104 and biotin-PEG12-peptide 105 according to the example 1, which is included in the experiment 1.

FIG. 3 shows a schematic view of a three-component composite 108 of iridium nanoparticle 107, avidin 104, and biotin-PEG12-peptide 105 according to the example 1, which is included in the experiment 1.

FIG. 4 is an electrophoretic photograph showing the results of the experiment 1.

DETAILED DESCRIPTION

The embodiment of the present invention is described below.

The present inventor has discovered that the peptide consisting of the amino acid sequence represented by SQMMGHMGHGNMNHMNHGGKFDFHH (SEQ ID NO: 01) recognizes iridium. The present invention is provided on the basis of this discovery.

The peptide consisting of the amino acid sequence represented by SEQ ID NO: 01 is derived from the amino acid sequence of the 382^nd to the 406^th amino acids of CueO. The term “CueO” means a multi-copper oxidase of Escherichia coli K-12 strain.

Experiment

The following experiments describe the present invention in more detail.

Experiment 1

The experiment 1 is comprised of the example 1 and the comparative example 1.

In the experiment 1, a pull-down method was performed. The pull-down method according to the experiment 1 is easily described below.

In the pull-down method according to the experiment 1, three-component composite of avidin, biotin-PEG12-peptide, and a iridium nanoparticle is formed in an aqueous solution. After the aqueous solution containing the three-component composite is subjected to a centrifugal separation, three-component composite are not collected as a supernatant. In other words, three-component composite is left in the aqueous solution as a precipitation (i.e., residue). Subsequently, the three-component composite is decomposed by heat treatment, and the solution is subjected to an electrophoresis. After the electrophoresis, a band of the subunit monomer of the avidin is observed.

On the other hand, two-component composite of avidin and biotin-PEG12 is not bound to a iridium nanoparticle. After an aqueous solution containing the two-component composite is subjected to a centrifugal separation, the two-component composite is eliminated as a supernatant. After the aqueous solution is heated, the aqueous solution is subjected to an electrophoresis. However, since the avidin has been eliminated as one chemical component contained in the supernatant, a band of the subunit monomer of the avidin is not observed.

In the experiment 1, the following solutions were prepared.

Biotin-PEG12-peptide solution

Biotin-PEG12 solution

Tris hydrochloric acid buffer solution

Avidin aqueous solution

Two-component composite aqueous solution of avidin and biotin-PEG12 (See FIG. 1)

Composite aqueous solution of avidin and biotin-PEG12-peptide (See FIG. 2)

Polyoxyethylene (20) sorbitan monolaurate aqueous solution

Buffer solution containing polyoxyethylene (20) sorbitan monolaurate

Sodium dodecylsulfate solution

Glycerol solution

Aqueous solution for an electrophoresis using a denaturing polyacrylamide gel

Iridium nanoparticle dispersion liquid

A detailed method for preparing these chemical reagents is described below.

(Preparation of a Biotin-PEG12-Peptide Solution)

The present inventor requested synthesis of a compound represented by the following formula (I) (hereinafter, referred to as “biotin-PEG12-peptide”) from Sigma Aldrich Japan Co., Ltd. A solid-phase synthesis method was used for the synthesis of the biotin-PEG12-peptide.

(Chem 01)
(SEQ ID NO: 1)
Biotin-PEG12-SQMMGHMGHGNMNHMNHGGKFDFHH (I)

The biotin-PEG12-peptide prepared by Sigma Aldrich Japan Co., Ltd. had a purity of 96.2%.

In the biotin-PEG12-peptide, as is clear from the formula (I), the N-terminal of the peptide consisting of the amino acid sequence represented by SEQ ID NO: 01 is chemically modified with biotin-polyethylene glycol.

The method for modifying the N-terminal of the peptide with biotin-polyethylene glycol is well known. As one example, EZ-Link NHS-PEG12-biotin (available from Thermo Fisher Scientific Corporation) may be used.

The EZ-Link NHS-PEG12-biotin has the following chemical formula (II).

##STR00001##

The term “NHS” means N-hydroxysuccinimide. NHS binds to an active ester group. When a peptide is added, the ester group activated by NHS reacts immediately with an NH₂ group located at the N terminal of the peptide or the side-chain of a lysine residue to form an amide bond.

The term “PEG” means polyethylene glycol. In more detail, PEG is represented by the following chemical formula (III).
—(—CH₂—CH₂—O)_n—  (III)

where n is a natural number.

It is desirable that the value of n is not less than 1 and not more than 20. The term “PEG12” means that the PEG where is n=12.

It is believed that the non-specific interaction between two molecules coupled through polyethylene glycol is prevented by the polyethylene glycol. In other words, it is believed that such a polyethylene glycol suppresses the non-specific interaction between two biological molecules chemically bonded to the both ends of the polyethylene glycol. This is because the two molecules are located far away from each other due to the polyethylene glycol interposed between the two molecules, as is clear from the chemical formula (II). For more detail, see Non Patent Literature 1, if necessary.

[Non Patent Literature 1] George et. al., “Effect of Surface Wettability on the Adsorption of Proteins and Detergents”, Journal of the American Chemical Society, Vol. 120, pp 3464-3473 (1998)

Therefore, in the chemical formula (I), the biotin molecule and the peptide consisting of the amino acid sequence represented by SEQ ID NO: 01 does not interact with each other due to PEG12.

(Preparation of the Biotin-PEG12-Peptide Solution)

Biotin-PEG12-peptide obtained from Sigma Aldrich Japan Co., Ltd. was dissolved with ultrapure water to prepare a biotin-PEG12-peptide solution having a concentration of 0.1 mM. The prepared biotin-PEG12-peptide solution was kept under a temperature of −30 degrees Celsius.

(Preparation of the Biotin-PEG12 Solution)

EZ-Link NHS-PEG12-Biotin (available from Thermo Fisher Scientific company) was dissolved with dimethylsulfoxide to prepare an EZ-Link NHS-PEG12-Biotin solution having a concentration of 10 mM.

Then, chemical reagents shown in Table 1 were mixed. The mixture liquid was left under a temperature of 25 degrees Celsius for one hour.

TABLE 1

Chemical reagent          Volume (unit: microliter)


10 mM NHS-PEG12-Biotin    20
1M Tris hydrochloric acid 20
buffer solution (pH: 8)
Ultrapure water           160

In this way, the biotin-PEG12 solution having a concentration of 1 mM was prepared. This biotin-PEG12 solution was diluted with water to prepare the biotin-PEG12 solution having a concentration of 0.1 mM.

(Preparation of the Tris Hydrochloric Acid Buffer Solution)

Hydrochloric acid was added in Tris buffer solutions to prepare the following four kinds of Tris hydrochloric acid buffer solutions shown in Table 2.

TABLE 2

1M Tris hydrochloric acid buffer solution (pH: 8)
100 mM Tris hydrochloric acid buffer solution (pH: 8)
10 mM Tris hydrochloric acid buffer solution (pH: 8)
1M Tris hydrochloric acid buffer solution (pH: 6.8)

(Preparation of the Avidin Aqueous Solution)

Avidin (Available from Thermo Fisher Scientific company, trade name: NeutrAvidin, 10 milligrams) was dissolved with ultrapure water to prepare 10 milligram/milliliter of an avidin aqueous solution. In FIG. 1, the avidin has a reference sign 101.

(Preparation of Two-Component Composite of Avidin and Biotin-PEG12)

The chemical reagents shown in the following Table 3 were mixed. In FIG. 1, the biotin-PEG12 has a reference sign 102. The mixture was left under a temperature of 23 degrees Celsius for two hours.

TABLE 3

                          Volume
Chemical reagent          (unit: microliter)


10 mg/mL of avidin        50
1M Tris hydrochloric acid 5
buffer solution (pH: 8)
Ultrapure water           95
0.1 mM biotin-PEG12       350

Subsequently, the mixture (500 microliters) was filtrated using a centrifugal ultrafiltration unit (available from Merck Ltd., trade name: Amicon Ultra-0.5, MWCO: 30,000) to obtain a residue. The centrifugal separation was performed under a temperature of 4 degrees Celsius at an rpm of 10,000×g for 20 minutes. In this way, the mixture was concentrated to obtain a concentrated liquid of approximately 50 microliters.

A Tris hydrochloric acid buffer solution (pH: 8, 450 microliters) having a concentration of 10 mM were mixed to the concentrated liquid. The concentrated liquid was subjected to a centrifugal separation under the same conditions as above again to obtain a concentrated liquid of approximately 50 microliters again. This was repeated once again.

The concentrated liquid was diluted with the Tris hydrochloric acid buffer solution (pH: 8) having a concentration of 10 mM to obtain an aqueous solution containing a two-component composite of avidin and biotin-PEG12. This aqueous solution had a volume of 500 microliter. In FIG. 1, two-component composite of avidin and biotin-PEG12 have a reference sign 103.

(Preparation of Composite of Avidin and Biotin-PEG12-Peptide)

The procedure similarly to that of the preparation of two-component composite of avidin and biotin-PEG12 was conducted, except that the chemical reagents shown in the following Table 4 were mixed instead of the chemical reagents shown in Table 3, so as to prepare an aqueous solution containing a composite of avidin and biotin-PEG12-peptide.

TABLE 4

                                 Volume
Chemical reagent                 (unit: microliter)


10 mg/mL of avidin               50
1M Tris hydrochloric acid buffer solution (pH: 8) 5
Ultrapure water                  95
0.1 mM biotin-PEG12-peptide (See the experiment 1) 350

In FIG. 2, the avidin has a reference sign 104. The biotin-PEG12-peptide has a reference number 105. The composite has a reference number 106.

(Preparation of Polyoxyethylene (20) Sorbitan Monolaurate Aqueous Solutions)

An aqueous solution of polyoxyethylene (20) sorbitan monolaurate (available from Affymetrix company, trade name: ANAPOE-20) having a concentration of 10 percent by weight was diluted with ultrapure water to prepare an aqueous solution of polyoxyethylene (20) sorbitan monolaurate having a concentration of 1 percent by weight. Similarly, an aqueous solution of polyoxyethylene (20) sorbitan monolaurate having a concentration of 0.1 percent by weight was prepared. Polyoxyethylene (20) sorbitan monolaurate may be used as a surfactant.

(Preparation of the Buffer Solution Containing Polyoxyethylene (20) Sorbitan Monolaurate)

The two kinds of buffer solutions shown in Table 5 were prepared.

TABLE 5

Buffer solution


10 mM Tris hydrochloric acid buffer solution (pH: 8) containing
0.1% by weight polyoxyethylene (20) sorbitan monolaurate
10 mM Tris hydrochloric acid buffer solution (pH: 8) containing
0.2% by weight polyoxyethylene (20) sorbitan monolaurate

(Preparation of the Sodium Dodecyl Sulfate Aqueous Solution)

Sodium dodecyl sulfate (available from Wako Pure Chemical Industries Ltd.) was dissolved with ultrapure water to prepare a sodium dodecyl sulfate aqueous solution having a concentration of 10% by weight.

(Preparation of the Glycerol Aqueous Solution)

Glycerol (available from Life Technologies Corporation) was dissolved with ultrapure water to prepare a glycerol aqueous solution having a concentration of 50% by weight.

(Preparation of an Aqueous Solution for an Electrophoresis Using a Denaturing Polyacrylamide Gel)

The chemical reagents shown in the following Table 6 were mixed to prepare an aqueous solution. Furthermore, approximately 1 milligram of bromophenol blue (powder) was added to the aqueous solution. Subsequently, the aqueous solution was stirred well. In this way, prepared was the aqueous solution for an electrophoresis using a denaturing polyacrylamide gel.

TABLE 6
Solution	Volume
1M Tris hydrochloric acid buffer solution (pH: 6.8)	0.55	milliliters
50% by weight glycerol solution	3.6	milliliters
2-mercaptoethanol	0.5	milliliters
10% by weight sodium dodecyl sulfate	4	milliliters
Ultrapure water	1.35	milliliters

(Preparation of the Iridium Nanoparticle Dispersion)

A dispersion liquid of the iridium nanoparticles each having a diameter of 1-4 nanometers (available from Renaissance Energy Research company, 0.5 milliliters) was mixed with ultrapure water (0.5 milliliters).

The mixture was subjected to a centrifugal separation under a temperature of 4 degrees Celsius at an rpm of 290,000×g for 2 hours. Subsequently, the supernatant was eliminated to obtain the concentrated liquid having a volume of 100 microliters. In this way, the mixture was concentrated.

Then, the 0.1% by weight polyoxyethylene (20) sorbitan monolaurate aqueous solution was added to the concentrated liquid. Subsequently, the concentrated liquid was subjected to a centrifugal separation again under the above-mentioned condition to remove the supernatant. In this way, a concentrated liquid having a volume of 100 microliters was obtained.

Again, the 0.1% by weight polyoxyethylene (20) sorbitan monolaurate was added to the concentrated liquid. Subsequently, the concentrated liquid was subjected to a centrifugal separation again under the above-mentioned condition to remove the supernatant. In this way, a concentrated liquid having a volume of 100 microliters was obtained again.

A 0.1% by weight polyoxyethylene (20) sorbitan monolaurate aqueous solution was added to the concentrated liquid to obtain the iridium nanoparticle dispersion liquid having a volume of 0.1 milliliter.

Example 1

The chemical reagents shown in the following Table 7 were mixed. The mixture was left under a temperature of 25 degrees Celsius for ten minutes.

TABLE 7

                                 Volume
Chemical reagent                 (unit: microliter)


10 mM Tris hydrochloric acid buffer solution (pH: 8) 24
10 mM Tris hydrochloric acid buffer solution (pH: 8) 25
containing 0.2% by weight of polyoxyethylene (20)
sorbitan monolaurate
Iridium nanoparticle dispersion  50
Composite aqueous solution of    1
avidin and biotin-PEG12-peptide

In FIG. 3, the iridium nanoparticles have a reference sign 107. The composite of Avidin and biotin-PEG12-peptide have a reference sign 106. The three-component composite of the iridium nanoparticles, avidin, and biotin-PEG12-peptide have a reference sign 108. The subunit monomer of the avidin obtained by heating the avidin has a reference sign 109. The biotin-PEG12-peptide after the heating has a reference sign 110.

The mixture was subjected to a centrifugal separation under a temperature of 4 degrees Celsius at an rpm of 290,000×g for 30 minutes. Subsequently, the supernatant was removed to eliminate the unreacted biotin-PEG12-peptide. In this way, a liquid mixture was concentrated to obtain a concentrated liquid (i.e., residue) having a volume of 10 microliters.

Then, the Tris hydrochloric acid buffer solution (pH: 8, 10 mM, 200 microliters) containing 0.1% by weight polyoxyethylene (20) sorbitan monolaurate was added to the concentrated liquid. Subsequently, the concentrated liquid was subjected to a centrifugal separation again under the above-mentioned condition to remove the supernatant. In this way, a concentrated liquid (i.e., residue) having a volume of 10 microliters was obtained.

The Tris hydrochloric acid buffer solution (pH: 8, 10 mM, 200 microliters) containing 0.1% by weight polyoxyethylene (20) sorbitan monolaurate was added to the concentrated liquid again. Subsequently, the concentrated liquid was subjected to a centrifugal separation again under the above-mentioned condition to remove the supernatant. In this way, a concentrated liquid (i.e., residue) having a volume of 10 microliters was obtained again. This concentrated liquid was brownish-red. Since a iridium nanoparticle dispersion liquid is brownish-red, it was confirmed by the naked eyes that the obtained concentrated liquid (i.e., residue) contained iridium nanoparticles.

The aqueous solution for an electrophoresis using a denaturing polyacrylamide gel was added to the concentrated iridium particle dispersion liquid. The volume of the aqueous solution was 20 microliters.

Subsequently, an ultrasonic wave was applied to the aqueous solution using an ultrasonic wave washer (available from AS ONE Corporation, trade name: USK-1A, configuration: High).

The concentrated iridium nanoparticle dispersion was heated under a temperature of 98 degrees Celsius for ten minutes to decompose the avidin molecule to avidin subunit monomers.

After the heating, the concentrated iridium nanoparticle dispersion was subjected to a centrifugal separation at an rpm of 10,000×g for one minute. In this way, a sample solution according to the example 1 was obtained.

Comparative Example 1

The procedure similarly to that of the example 1 was conducted, except that the biotin-PEG12 was used instead of the biotin-PEG12-peptide. In this way, a sample solution according to the comparative example 1 was obtained.

(Electrophoresis in the Experiment 1)

These two kinds of sample solutions according to the example 1 and the comparative example 1 were subjected to electrophoresis. The detail of the electrophoresis is described below.

A polyacrylamide gel (pre-cast gel, available from Bio-Rad Laboratories, Inc., trade name: 12% Mini-PROTEAN TGX) was equipped to an electrophoresis tank. As an electrophoretic buffer, a pre-mixed buffer (available from Bio-Rad Laboratories, Inc., trade name: premix buffer 10× Tris/glycine/SDS) was diluted ten times with extrapure water. This diluted solution was poured to the electrophoresis tank.

The two sample solutions (for each 15 microliters) according to the example 1 and the comparative example 1 were added to the wells provided at the top of the polyacrylamide gel.

A benchmark protein ladder (available from Life Technologies Corporation, 5 microliters) was added the well provided at the top of the polyacrylamide gel as a molecular weight marker.

The electrophoresis was performed under a constant voltage of 150 volts.

When the Bromophenol Blue contained in the aqueous solution was moved by the electrophoresis to the neighborhood of the bottom of the polyacrylamide gel, the electrophoresis was stopped. Subsequently, a CBB stain was performed with a CBB stain kit (available from Bio-Rad Laboratories, Inc., trade name: R-250 stain & destain kit).

The image of the stained polyacrylamide gel was read with a flatbed scanner (Available from CANON. Inc., trade name: CanoScan D2400U). The band of the subunit monomer of the avidin was quantified using image processing software ImageJ (available from National Institutes of Health) on the basis of the read image.

FIG. 4 shows the electrophoretic results.

As shown in FIG. 4, a clear band was observed in the example 1. On the other hand, such a clear band was not observed in the comparative example 1.

According to the image processing software, the band according to the example 1 contained 3.9 times as many subunit monomers of avidin as the band according to the comparative example 1.

From the electrophoresis result shown in FIG. 4, namely, the result by a pull-down method, it was found that Biotin-PEG 12-peptide binds to a iridium nanoparticle to form an aggregate (i.e., precipitate). Since the biotin and the peptide do not interact due to PEG 12, it was found that the peptide consisting of the amino acid sequence represented by SEQ ID NO: 01 binds to iridium. In other words, it was found that the peptide consisting of the amino acid sequence represented by SEQ ID NO: 01 recognizes iridium.

INDUSTRIAL APPLICABILITY

The present invention provides a peptide capable for binding to iridium.

REFERENCE SIGNS LIST

• 101, 102: precipitate
• 101, 104: avidin
• 102: biotin-PEG 12
• 103: two-component composite of avidin and biotin-PEG12
• 105, 110: biotin-PEG12-peptide
• 106: composite of avidin and biotin-PEG12-peptide
• 107: iridium nanoparticle
• 108: three-component composite of iridium nanoparticle, avidin, and biotin-PEG 12-peptide
• 109: subunit monomer of avidin

Claims

1. A method for binding a peptide to iridium, the method comprising steps of:

mixing the iridium with a solution containing the peptide consisting of an amino acid sequence of seq ID NO: 01 so as to bind the peptide to the iridium.

2. A composite comprising a peptide consisting of an amino acid sequence of seq ID NO: 01 and iridium, wherein the peptide is bound to the iridium.